Silychristin and isosilychristin from the fruits

Tài liệu nghiên cứu về "Silychristin and isosilychristin from the fruits".

Journal of Chemistry, Vol 45 (1), P 106 - 109, 2007

SILYCHRISTIN AND ISOSILYCHRISTIN FROM THE FRUITS OF

SILYBUM MARIANUM (L.) GAERTN

Received 31 May 2006

TRINH THI DIEP1, PHAN VAN KIEM2, NGUYEN THUONG DONG1, NGUYEN HUU TUNG2,

BUI THI BANG1, CHAU VAN MINH2, ALESSANDRA BRACA3

1 National Institute of Medicinal Materials, Ministry of Health

2 Institute of Natural Products Chemistry, VAST 3

Department of Bioorganic Chemistry and Biopharmaceutics University of Pisa, Italia

SUMMARY

By various chromatography methods, two flavonolignan silychristin (1) and isosilychristin (2)

were isolated from the fruits of Silybum marianum (L.) Gaertn cultivated in the North of Vietnam Their structures were elucidated by analyses of the NMR (1D-, 2D-NMR) and ESI

spectra This is the first report of both 1 and 2 from S marianum cultivated in Vietnam

I - INTRODUCTION

In previous papers, we have reported the

isolation and structural elucidation of

flavonolignan, flavonoid, and lignan

compositions of the fruits of Silybum marianum

(L.) Gaertn cultivated in the North of Vietnam

and used in folk medicine [1 - 4] Here, we

report the isolation and structural determination

of two flavonolignan silychristin (1) and

isosilychristin (2) isolated from the fruits of

Silybum marianum (L.) Gaertn cultivated in the

North of Vietnam The structures were

elucidated by analyses of the NMR and ESI

spectra, and by the reported data This is the

first report of both 1 and 2 from S marianum

cultivated in Vietnam

II - EXPERIMENTAL

1 General experimental procedures

The Electronspray Ionization (ESI) mass

spectrum was obtained using a AGILENT 1100

LC-MSD Trap spectrometer The NMR spectra

were recorded on a Bruker AM500 FT-NMR

spectrometer using TMS as the internal standard Column chromatography (CC) was performed on silica gel (Kieselgel 60, 70 - 230 mesh and 230 - 400 mesh, Merck) or YMC

RP-18 resins (30 - 50 µm, FuJisilisa Chemical Ltd.) Thin layer chromatography (TLC) was performed on DC-Alufolien 60 F254 (Merck 1.05715) or RP18 F254s (Merck) plates

2 Plant material

The fruits of Silybum marianum (L.) Gaertn

were collected in Sapa, Lao Cai Province in June, 2004 and were identified by Dr Nguyen Tap, Department of Botany and Medicinal Plant Resources, National Institute of Medicinal Materials

3 Extraction and isolation

Air-dried and powdered fruits of Silybum marianum (L.) Gaertn (200 g) were defatted with

petroleum and then extracted with methanol After removal of the solvent under vacuum, the residue (5.8 g) was obtained, which was then repeated chromatographed on silica gel columns

to get 1 (30 mg) as colorless amorphous powder and 2 (50 mg) as yellow crystals

III - RESULTS AND DISCUSSION

Compound 1 was obtained as colourless

amorphous powder from methanolic extract of

the fruits of S marianum (L.), mp 174 - 176oC

The 1H-NMR spectrum of 1 exhibited two

doublets at H5.85 and 5.90 ppm (J = 1.5 Hz),

two doublets at H 6.82 and 6.87 ppm, three

other aromatic protons at H 6.79 (d, J = 8.0

Hz), 6.81 (dd, J = 8.0, 1.0 Hz) and 6.99 (d, J =

1.0 Hz) Two doublet of doublets of two protons

at trans configuration were at 5.00 (dd, J = 11.5, 2.5 Hz) and 4.49 (dd, J = 11.5, 5.5 Hz) [5], a doublet at 5.46 (J = 7.0 Hz), a multiplet

at 3.49 The methylene group bearing oxygen

atom was at 3.64 (dd, J = 10.0, 10.5 Hz) and 3.71 (dd, J = 10.5, 5.5 Hz), and methoxyl group

was at 3.75 as a singlet signal All the 1H-NMR

data suggested the flavonolignan type of 1,

which was similar to the isolated compounds from the same sources [1, 2]

Table 1: The NMR data of 1

C b,d

H c,d (J in Hz)

2’ 116.6 115.26 6.87 (d, 1.5)

6’ 116.9 115.58 6.82 (d, 1.5)

89.1 86.96 5.46 (d, 7.0)

64.8 62.94 3.64 (dd, 10, 10.5); 3.71 (dd, 5.5, 10.5)

2” 110.6 110.43 6.99 (d, 1.0)

5” 116.2 115.26 6.79 (d, 8.0)

6” 119.7 118.64 6.81 (dd, 1.0, 8.0)

OCH3 56.4 55.64 3.75 (3H, s)

a

C of silychristin [5], b

125 MHz, c

500 MHz, d

Measured in DMSO-d 6

OH

O

O

HO

OH

2 3 4 5

6

7 8 9

10

1' 2' 3' 4' 5' 6'

OH

CH2OH

OH OCH3

1"

2"

3"

4"

5"

6"

1

O

OH O

HO

OH

2 3 4 5 6

7 8 9 10

1' 2' 3'4' 5' 6'

1"

2"

3" 4"

5"

6"

O

HOH2C

OH

2

Fig.1 The structures of 1 & 2

The 13C-NMR spectrum of 1 showed the

signals of 25 carbons including 12 quaternary,

11 methine, 1 oximethylene and 1 methoxyl

carbons, suggesting a flavonolignan compound

methylene bearing oxygen atom was at 62.94

and methoxyl group was at 55.64 All NMR

assignments of 1 were made from analysis of

HSQC, HMBC spectra and by comparison with

those of isolated compound

(dehydrosily-christin) [3] as well as with those of silychristin

reported in the literature [5] In the HMBC

spectrum, H-2 ( 5.00) correlated with C-3 (

115.26), and H-3 ( 4.49) had only correlations

with C-2 ( 83.2) and C-1’ (128.99) confirming

the position of two oximethine carbons at C-2

and C-3 In addition, the H-C long-range

110.43)/C-(62.94), as well as the H-C long-range

3.49) and carbons C1” ( 132.38)/C- (62.94)

also confirming the positions of C- , C- and

groups The selected H-C correlations in the

HMBC spectrum of 1 were shown in Fig 2

Furthermore, the negative ESI mass spectrum of

1 exhibited an ion peak at m/z 481 [M-H]+with

strongest intensity, corresponding to the

molecular formula of C25H22O10 From the above

data, compound 1 was determined to be

silychristin, which was first isolated from

Silybum marianum (L.) Gaertn cultivated in the

North of Vietnam This compound also was reported to be inhibitor of horseradish peroxidases and lipoxygenase and antihepatotoxic agent [5]

Compound 2 was obtained as yellow

crystals from methanolic extract of the fruits of

S marianum (L.), mp 155 - 157oC and had

similar NMR spectra as compound 1, suggesting

the same flavonolignan type 25 carbons corresponding to 25 carbon signals were

(including 12 quaternary, 11 methine, 1

oximethylene and 1 methoxy carbons as 1) Detailed comparison from NMR spectrum of 2 with those of 1, especially at C-2, C-3, C- and

C- showed that 2 must be a derivative of 1, as

isosilychristin, which was also isolated from

Silybum marianum (L.) Gaertn [6] The ESI

mass spectrum of 2 was taken confirming the

molecular formula of C25H22O10 of 2 from the

appearance of an ion peak at m/z 483 [M+H]+in

the positive and an ion peak at m/z 481 [M-H]+

in the negative spectra All NMR assignments

of 2 were made carefully from HSQC and HMBC and from the comparison with those of 1

as shown in table 2 The H-C long-range correlations in the HMBC were shown in Fig.2

further confirming the structure of 2 as

isosilychristin, which also was first isolated

from Silybum marianum (L.) Gaertn cultivated

the North of Vietnam

Table 2: The NMR data of 2

C Ca,b

H a,c (J in Hz)

2 79.87 5.17 (d, 12.0)

3 71.48 4.66 (dd, 12.0, 6.0)

-6 96.10 5.92 (d, 1.5)

-8 95.03 5.87 (d, 1.5)

2’ 119.42 6.95 (d, 8.0)

3’ 116.08 6.74 (d, 8.0)

C Ca,b

H a,c (J in Hz)

86.36 5.57 (d, 2.0) 51.97 3.68 (m) 63.49 3.46 (dd, 10, 10.5)

3.72 (dd, 5.5, 10.5)

2” 110.28 6.86 (d, 1.5)

5” 115.15 6.71 (d, 8.5) 6” 118.48 6.76 (dd, 8.5, 1.5) OCH3 55.59 3.71 (3H, s)

a

Measured in DMSO-d 6 , b

125 MHz, c

500 MHz.

O

OH

O

O

HO

OH

2

4 5

6

7 8

9

10

1' 2'

3' 4'

5'

OH

CH2OH

OH

OCH3

1"

2"

3"

4"

5"

6"

O

OH O

HO

OH

3 4 5 6

7 8 9 10

2'

3' 4' 5'

1"

2"

3" 4"

5" 6" O

HOH2C

OH

Figure 2: H-C long-range correlations in the HMBC of 1 and 2 Acknowledgements: The authors wish to thank

Mr Dang Vu Luong, the NMR Lab., Institute of

Chemistry, Vietnamese Academy of Science and

Technology for recording the NMR spectrum,

and Dr Nguyen Tap, Department of Botany and

Medicinal Plant Resources, National Institute

of Medicinal Materials for the plant

identification This study was supported by a

grant from the Vietnam- Italia international

cooperation project

REFERENCES

1 Vo Van Chi Vietnamese Medical Plant

Dictionary, Ha Noi Medicine Pub (1997)

2 T T Diep, N T Dong, B T Bang, C V Minh, P V Kiem Journal of Medicinal Materials, Vol 10(6), 175 - 178 (2005)

3 T T Diep, N T Dong, B T Bang, C V Minh, P V Kiem Journal of Medicinal Materials, Vol 11(1), 9 - 13 (2006)

4 T T Diep, N T Dong, B T Bang, C V Minh, P V Kiem Vietnamese Journal of Chemistry, 2006 (accepted)

5 H Tanaka, M Hiroo, K Ichino, K Ito Chem Pharm Bull., Vol 37(6), pp 1441 -

1445 (1989)

6 M Kalonga, Z Naturforsch., B, Vol 36,

262 - 266 (1981)

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